The present invention relates to the field of nucleoside analogs.
Ribavirin (1-xcex2-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) is a nucleoside analog that has demonstrated efficacy in treating viral diseases both as monotherapy (respiratory syncytial virus, Hall, C. B.; McBride, J. T.; Walsh, E. E.; Bell, D. M.; Gala, C. L.; Hildreth, S.; Ten Eyck, L. G.; W. J. Hall. Aerosolized Ribavirin treatment of infants with respiratory syncytial viral infection. N. Engl. J. Med. 1983, 308, 1443-1447), and in combination therapy with interferon-alpha (hepatitis C virus, Reichard, O.; Norkrans, G.; Fryden, A.; Braconier, J-H.; Sonnerborg, A.; Weiland, O. Randomized, double blind, placebo controlled trial of interferon alpha 2B with and without Ribavirin for chronic hepatitis C. Lancet 1998, 351, 83-87).
Recently reported studies indicate that the in vivo utility of Ribavirin can result not only from direct inhibition of viral replication, but also from its ability to enhance T cell-mediated immunity (Hultgren, C.; Milich, D. R.; Weiland, O.; Sxc3xa4llberg, M. The antiviral compound Ribavirin modulates the T helper Type1/Type2 subset balance in hepatitis B and C virus-specific immune responses. J. Gen. Virol. 1998, 79, 2381-2391; Ning, Q.; Brown, D.; Parodo, J.; Cattral, M.; Fung, L.; Gorczynski, R.; Cole, E., Fung, L.; Ding, J. W.; Liu, M. F.; Rotstein, O.; Phillips, M. J.; Levy, G. Ribavirin inhibits viral-induced macrophage production of tumor necrosis factor, interleukin-1, procoagulant activity fgl2 prothrombinase and preserves Th1 cytokine production but inhibits Th2 cytokine response. J. Immunol. 1998, 160, 3487-3493; Martin, M. J.; Navas, S.; Quiroga, J. A.; Pardo, M.; Carreno, V. Effects of the Ribavirin-interferon alpha combination on cultured peripheral blood mononuclear cells from chronic hepatitis C patients. Cytokine 1998, 79, 2381-2391). This immunomodulatory effect of Ribavirin is demonstrable in vitro by measuring the levels of Type 1 cytokines produced by activated T cells from both humans and mice (Tam, R. C.; Pai, B.; Bard, J.; Lim, C.; Averett, D. R.; Phan, U. T.; Milovanovic, T. Ribavirin polarizes human T cell responses towards a Type 1 cytokine profile. J. Hepatol. 1999, 30, 376-382) and by other measures. The induction of a Type 1 cytokine bias by Ribavirin is functionally significant in vivo in murine systems (Tam, R. C.; Lim, C.; Bard, J.; Pai, B. Contact hypersensitivity responses following Ribavirin treatment in vivo are influenced by Type 1 cytokine polarization, regulation of IL-10 expression and costimulatory signaling. J. Immunol. 1999, 163, 3709-3717).
Mammalian immune systems contain two major classes of lymphocytes: B lymphocytes (B cells), which originate in the bone marrow; and T lymphocytes (T cells) that originate in the thymus. B cells are largely responsible for humoral immunity (i.e., antibody production), while T cells are largely responsible for cell-mediated immunity. T cells are generally considered to fall into two subclasses, helper T cells and cytotoxic T cells. Helper T cells activate other lymphocytes, including B cells, cytotoxic T cells, and macrophages, by releasing soluble protein mediators called cytokines that are involved in cell-mediated immunity. As used herein, lymphokines are a subset of cytokines. Helper T cells are also generally considered to fall into two subclasses, Type 1 and Type 2. Type 1 cells produce interleukin 2 (IL-2), tumor necrosis factor (TNFxcex1) and interferon gamma (IFNxcex3), and are responsible primarily for cell-mediated immunity such as delayed type hypersensitivity and antiviral immunity. In contrast, Type 2 cells produce interleukins, IL4, IL-5, IL-6, IL-9, IL-10 and IL-13, and are primarily involved in assisting humoral immune responses such as those seen in response to allergens, e.g. IgE and lgG4 antibody isotype switching (Mosmann, 1989, Annu Rev Immunol, 7:145-173).
As used herein, the terms Type 1 and Type 2 xe2x80x9cresponsesxe2x80x9d are meant to include the entire range of effects resulting from induction of Type 1 and Type 2 lymphocytes, respectively. Among other things, such responses include variation in production of the corresponding cytokines through transcription, translation, secretion, and possibly other mechanisms, increased proliferation of the corresponding lymphocytes, and other effects associated with increased production of cytokines, including motility effects.
Previous application Ser. Nos. (09/291903, 09/471513, 60/164365, 60/164366, 60/172097, 60/175111, and 60/189672), each of which is incorporated herein by reference, relate to aspects of our recent discoveries involving the effect of various nucleosides (which are defined herein to include derivatives and analogs of native nucleosides) on selectively modulating lymphocyte responses relative to each other. Among other things, we have shown that either of the Type 1 and Type 2 responses can be selectively suppressed while the other is either induced or left relatively unaffected, and either of the Type 1 or Type 2 responses can be selectively induced while the other is either suppressed or left relatively unaffected. We have also discovered the surprising fact that some nucleosides effective in selectively modulating Type 1 and Type 2 responses relative to one another tend to have a bimodal effect. Among other things, some nucleosides that tend to generally suppress or induce both Type 1 and Type 2 activity at a relatively higher dose tend to selectively modulate Type 1 and Type 2 relative to each other at relatively lower doses.
Viramidine(trademark) (1-xcex2-D-ribofuranosyl-1,2,4-triazole-3-carboxamidine hydrochloride) has been shown active in ten different virusesxe2x80x94comparable to Ribavirin. (J. T. Witkowski, R. K. Robins, G. P. Khare, R. W. Sidwell, J. Med. Chem., 16, 935-937, 1973; R. W. Sidwell, J. H. Huffman, D. L. Barnard, D. Y. Pifat, Antiviral Research, 10, 193-208, 1988; B. Gabrielsen, M. J. Phelan, L. Barthel-Rosa, C. See, J. W. Huggins, D. F. Kefauver, T. P. Monath, M. A. Ussery, G. N. Chmumy, E. M. Schubert, K. Upadhya, C. Kwong, D. A. Carter, J. A. Secrist III, J. J. Kirsi, W. M. Shannon, R. W. Sidwell, G. D. Kini, R. K. Robins, J. Med. Chem., 35, 3231-3238, 1992). In addition, Viramidine(trademark), like Ribavirin, is an inhibitor of IMP dehydrogenase (R. C. Willis, R. K. Robins, J. E. Seegmiller, Molecular Pharmacology, 18, 287-295, 1980). Furthermore, preliminary toxicology studies suggest that Viramidine(trademark) is less toxic than Ribavirin (D. Y. Pifat, R. W. Sidwell, P. G. Canonico, Antiviral Research, 9, 136, 1988). Also, recent studies at our lab (R. Tam, K. Ramasamy, ICN Pharmaceuticals, Inc., unpublished results, 1999) revealed that Viramidine(trademark) and Ribavirin exhibit similar immunomodulatory properties. These results coupled with low bioavailability and the toxicity associated with Ribavirin prompt us not only to develop Viramidine(trademark) for other viral diseases but also to prepare other derivatives of Viramidine(trademark), including the synthesis of prodrugs of Viramidine(trademark), and screen them as potential antiviral agents.
Ribavirin and Levovirin are similar with respect to structure, except that Levovirin is in the L-configuration of the compound and has a substantially reduced toxicity. For example, while oral administration of Ribavirin in rats at 180 mg/kg over four weeks produced significant hemolytic anemia and leukopenia, Levovirin did not produce any observable clinical pathology. Furthermore, it is contemplated that treatment of a viral disease with Levovirin is predominantly based on the modulation of the Th1/Th2 balance towards a Th1 dominated response, and not predominantly based on a direct antiviral effect. The term xe2x80x9cdirect antiviralxe2x80x9d effect or activity as used herein refers to an immediate effect or activity of a drug on viral assembly or replication. In contrast, a reduction of viral activity or replication that is at least in part mediated by one or more components of the immune system is not considered a xe2x80x9cdirect antiviralxe2x80x9d effect or activity. Likewise, it should be appreciated that a relative reduction of the Th2 response during a treatment may be especially advantageous in diseases that are correlated with an increased Th2 response (e.g., HCV infection).
The effect of other nucleoside analogs on selectively modulating lymphocyte responses relative to each other has not been previously studied or documented. We have discovered that the bimodal effect, or selective modulation of Type 1 and Type 2 responses relative to one another, also occurs after administration of other nucleoside analogs, such as pro-drug forms of the compounds.
There are many barriers to overcome in developing biologically active compounds into clinically useful agents. Many potent biologically active compounds never become clinically useful agents because of their undesirable biopharmaceutical properties which include low bioavailability due to low permeability through biological barriers, such as the blood brain barrier (BBB) and the intestinal barrier. Although many factors affect the bioavailability of a drug, the undesirable physicochemical properties (e.g., charge, lipophilicity, hydrogen bonding potential, size) of many drugs is probably one of the most commonly encountered factors that hinder the permeation of drugs through biological barriers. Therefore, optimization of the physicochemical characteristics (charge, lipophilicity, hydrogen bonding potential, size) of a drug is probably the most likely general strategy to facilitate the transport of drugs through such membrane barriers.
To optimize the physicochemical properties of drugs, one possible strategy is that of prodrugs. (H. Bundgaard, Design of Prodrugs, Elsevier, Amsterdam, 1985; N. Bodor, L. Prokai, W. M. Wu, H. Farag, S. Jonalagadda, M. Kawamura, J. Simpkins, Science, 257, 1698-1700, 1992; H. E. Taylor, K. B. Sloan, J. Pharm. Sci, 87, 5-20, 1998). The term prodrug is used to describe an agent, which must undergo chemical or enzymatic transformation to the active or parent drug after administration, so that the metabolic product or parent drug can subsequently exhibit the desired pharmacological response. By derivatizing certain polar functional groups in small organic molecules transiently and bioreversibly, the undesirable physicochemical characteristics (e.g., charge, hydrogen bonding potential) of these groups have been xe2x80x9cmaskedxe2x80x9d without permanently altering the pharmacological properties of the molecules. This strategy has been very successfully used in cases where the prodrug derivatization involves converting a carboxyl or a hydroxyl functional group into an ester, which can be readily hydrolyzed in vivo either chemically, or enzymatically.
Thus, although various prodrugs and modifications of triazole-nucleosides are known in the art, several potential disadvantages (e.g., limited bioavailability or limited selectivity towards a diseased cell and/or organ) still remain. Therefore, there is still a need to provide improved compositions and methods for triazole nucleosides.
The present invention is directed to nucleoside analogs and related compounds, including their prodrugs and metabolites, and their therapeutic uses and synthesis.
In one aspect of the invention, there are provided nucleosides, nucleoside analogs and nucleoside prodrugs of the generalized Formula below, in which the sugar is either in the L- or D-configuration:
R-Nu 
and wherein Nu is a nucleoside or nucleoside analog, and R, which may or may not be present, comprises a ligand, otherwise termed a substituent, that is designed to modify the nucleoside through modification of the sugar, the base, or in some cases both the sugar and the base.
In one aspect of the invention, there are provided nucleoside analogs and prodrugs of Formula 1, in which the sugar is either in the L- or D-configuration: 
and wherein A, X, Y, and D are independently selected from N or Cxe2x80x94R9; R9 is independently H, halogen, lower alkyl, alkenyl, alkynyl, amino, CN, SH, CHO, COOH, CH2OH, or hydroxyl; Z is O, CH2 or S; Rxe2x80x2 and Rxe2x80x3 are independently selected from H, hydroxyl, protected hydroxyl, or halogen; R1, R2, R3, R4, and R5, are independently selected from H, halogens, CN, CH2OH, lower alkyl, vinyl or acetylene; when R2 is hydroxyl, then, Rxe2x80x3 that is attached to the same carbon as that of R2 is not halogen; when R3 is hydroxyl, then, Rxe2x80x2 that is attached to the same carbon as that of R3 is not halogen; R6 is independently selected from H, hydroxyl, protected hydroxyl, xe2x80x94CH2OH, xe2x80x94CH2PO(OH)2xe2x80x94, O-amino acids, O-retinoic acid, O-cholesteral, O-cholic acid, O-coumarinic acid, O-salicylic acid, O-succinic acid, O-bile acid, O-lipids, Oxe2x80x94P(O)xe2x80x94(Oxe2x80x94CH2xe2x80x94CH2xe2x80x94Sxe2x80x94COxe2x80x94CH3)2; O-steroids; Boranophosphate, Boranophosphate derivatives, O-monophosphate derivatives, O-diphosphate derivatives or O-triphosphate derivatives; R7 is independently selected from H, alkyl, CH3COOxe2x80x94, CH3COO-Phenyl-CH2xe2x80x94Oxe2x80x94COxe2x80x94, phenyl, xe2x80x94(CH2)n-COOH, coumarinic acid, salicylic acid, dithiosuccinoyl derivatives, reductase mediated cleavable groups, phosphonoformic acid or phosphoramidates groups; R8 is independently selected from H, H*HCl, H*HBr, lower alkyl, carbamate, phenyl, CH3COOxe2x80x94, CH3COO-Phenyl-CH2xe2x80x94Oxe2x80x94COxe2x80x94, phenyl, or xe2x80x94(CH2)n-COOH; R7 and R8 may form a cyclic structure or be independently an amino acid.
In another aspect of the invention, there are provided nucleoside analogs and prodrugs of Formula 2, in which the sugar is either in the L- or D-configuration: 
wherein X is O, NH; R1 is H or a masking group of the amino group; R2 is selected from H, HC(O)xe2x80x94, Boranophosphate, Boranophosphate derivative, Rxe2x80x2xe2x80x94C(O)xe2x80x94, wherein Rxe2x80x2 is substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, or R2 is a protected or unprotected monophosphate, diphosphate, or triphosphate, and R3 is independently H or C1-C18 acyl.
In another aspect of the invention, there are provided nucleoside analogs and prodrugs of Formula 3, in which the sugar is either in the L- or D-configuration: 
wherein R1 is a masking group having any of the following structures: 
where X is O or S; and wherein R is C1-C18 alkyl, alkenyl, alkynyl, aryl, and aralkyl, straight or branched, and wherein the 5xe2x80x2-OH group may further be modified to form a monoboranophosphate radical, diboranophosphate radical, triboranophosphate radical, stabilized monophosphate radical, stabilized diphosphate radical, or stabilized triphosphate radical.
In another aspect of the invention, there are provided nucleoside analogs and prodrugs of Formula 4, in which the sugar is either in the L- or D-configuration: 
wherein X is O or NH; Y is OR2 or BH3; R1 is H or a masking group of the amino group; and R2 is a masking group of the phosphate, preferably having any of the following structures: 
where X is O, or S; and R is C1-C18 alkyl, alkenyl, alkynyl, aryl, aralkyl straight or branched.
In another aspect of the invention, there are provided nucleoside analogs and prodrugs of Formula 5, in which the sugar is either in the L- or D-configuration: 
where X is O or NH, R1 is H or a masking group; R2 is phosphate group with a masking group having any one of the following structures: 
where R is substituted or unsubstituted C1-C18 alkyl, alkenyl, alkynyl, aryl, and aralkyl, (which may be straight or branched), or halogen, and wherein M is selected from alkyl, alkenyl, alkynyl, aralkyl, aryl, and a group of hydrophobic compounds, including cholesterol, vitamin D and various derivatives thereof, and cholic acid derivatives bearing a linker which can be covalently attached to the carbonyl atom of the cholic acid.
In yet another aspect of the invention, there are provided nucleoside analogs and prodrugs of Formula 6: 
wherein X is a phosphate or boranophosphate, and wherein Y is null or an acid to form a pharmacologically acceptable salt.
In still another aspect of the invention, there are provided nucleoside analogs and prodrugs of Formula 7 in which the sugar may be in D- or L-configuration 
In yet another aspect of the invention, a pharmaceutical composition comprises a therapeutically effective amount of any one or a combination of Formulas 1-7, or a pharmaceutically acceptable ester or salt thereof admixed with at least one pharmaceutically acceptable carrier.
In a further aspect of the invention, a compound according to any one of Formulas 1-7 is used in the treatment of any condition, which responds positively to administration of the compound, and according to any formulation and protocol which achieves the positive response. Among other things, it is contemplated that compounds of Formulas 1-7 may be used to treat an infection, an infestation, a cancer, tumor or other neoplasm, giant cell arteritis, or an autoimmune disease.